Siemens sinumerik 808d Programming And Operating Manual page 27

Figure 1-2
Absolute dimensioning G90
With absolute dimensioning, the dimensioning data refers to the zero of the coordinate
system currently active (workpiece or current workpiece coordinate system or machine
coordinate system). This is dependent on which offsets are currently active: programmable,
settable, or no offsets.
Upon program start, G90 is active for all axes and remains active until it is deselected in a
subsequent block by G91 (incremental dimensioning data) (modally active).
Incremental dimensioning G91
With incremental dimensioning, the numerical value of the path information corresponds to
the axis path to be traversed. The leading sign indicates the traversing direction.
G91 applies to all axes and can be deselected in a subsequent block by G90 (absolute
dimensioning).
Specification with =AC(...), =IC(...)
After the end point coordinate, write an equality sign. The value must be put in round
brackets.
Absolute dimensioning is also possible for center points using =AC(...). Otherwise, the
reference point for the circle center is the circle starting point.
Programming example
N10 G90 X20 Z90
N20 X75 Z=IC(-32)
N180 G91 X40 Z2
N190 X-12 Z=AC(17)
Turning Part 2: Programming (Siemens instructions)
Programming and Operating Manual, 05/2012, 6FC5398-5DP10-0BA0
different dimensioning types in the drawing
; Absolute dimensions
; X-dimensions remain absolute, incremental Z dimension
; Switch-over to incremental dimensioning
; X-remains incremental dimensioning, Z-absolute
Programming principles
1.2 Positional data
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